It is known that for use in a camera, a spool of filmstrip material, film, is enclosed in a light tight film cartridge. Typically, the exposed, unexposed or developed status of the filmstrip material is indicated by the angular positioning of the spool within the cartridge. An indicator on the spool in communication with the spool drive, reveals the film status.
During manufacturing, film manufacturers set the spool in the film cartridge in a first position to indicate that the filmstrip therein is unexposed. When installed in a camera, the cartridge must be sealed in a light tight manner before the film is exposed during picture taking. A camera access door is usually used to secure the cartridge in the camera and to provide a light tight seal. Mechanisms for securing the access door during the exposure sequence are well known.
After the film exposure sequence is completed, the film is completely rewound into the cartridge and the operator removes the cartridge from the camera. As part of the cartridge handling requirements, the spool must be parked at a specific position in the cartridge, different from the unexposed position set by the manufacturer, to indicate that the film in the cartridge has been exposed. In certain cameras, the operator winds the film onto the spool manually. With these cameras the operator is required to park the rewind knob at a specific position that corresponds to the exposed position. A problem with these cameras, however, is that no simple mechanism is available for securing the access door until the spool is parked properly in its cartridge.